1. Field of the Invention
The present industrial invention concerns a device for the detection of the optical parameters of a laser beam.
2. Description of the Related Art
Laser sources are widely employed in different fields: industrial, scientific, medical, etc.
In all applications, in order to obtain a constant work quality, it is very important to detect most of the optical parameters that influence a determined process.
Detection devices generally used only evaluate the average power of the laser beam. Such devices consist of a sensing element that is capable of transforming the incident optical power into an electric signal, that is then adequately displayed.
One of the principles on which such detecting devices are based upon is the calorimetric one, in which a laser beam, incident on an absorbing material internal to the detection device, increases its temperature. Through the use of conventional temperature sensors, as thermopiles, properly applied to the absorber element on the surface opposite to the one hit by the laser beam, the variation in temperature is transformed into a variation of voltage (or current).
Other known detection devices use a photosensitive element made of a semiconductor material. In this case, the photons of the laser beam hit the photosensitive element that, thus excited, generates an electric signal.
The specific type of detection device to be utilised depends on the type of laser source and on its power. For example, a typical detection device for CO2 laser and for high power lasers is the one with thermopile detectors, even if a device of this kind is less sensitive and slower than a semiconductor device.
In industrial applications the device for the detection of the power of a laser beam is generally located behind the high reflectivity mirror of the laser resonant cavity; in other applications, such as the scientific, medical ones etc., said device can also be located along the path of the beam coming from the laser source.
In both types of the aforementioned detection devices, the sensing element, made of absorbing material in case of the calorimetric type and of photosensitive material in case of the semiconductor type, can be sectioned into several parts, generally four quadrants, in order to be able to detect, in addition to the average power of the laser beam, also the displacements of the centroid of the intensity distribution of the laser beam itself. Devices of this kind are referred to as "four quadrant devices".
By using any one of the detection devices as described, it is not possible to establish, without an accurate investigation that implies to stop and to inspect visually several components of the system, if possible malfunctions should be attributed to a degeneration of the characteristics of the laser beam being generated or to a deterioration of the optical line external to the laser source itself, which conveys the beam to the working point.